Thornton suffered the injury during a first-period fight with John Scott on Thursday against Buffalo. The 6-foot-8-inch, 270-pound Scott flattened Thornton with a flurry of rights while keeping his opponent away with his left hand.

Thornton was wobbly as he got to his skates, and was guided to the penalty box by linesman Michel Cormier. Thornton served the five-minute major, but then went to the dressing room. He didn’t return.

“Unfortunately, there’s always a risk in that job,” coach Claude Julien said of Thornton’s fighting role. “He took on a pretty big man as we all know, 6-8 and maybe around 280 pounds. He handled himself as best as he could. Those things are going to happen. At the end of the day, he still was willing to do it for his team. Not only do we lose a guy who does it well, but he’s a good teammate and he’s great in the dressing room. Hopefully, we get him back soon.”

Thornton has been a Bruin since 2007, and it is the first time he has officially been diagnosed with a concussion during his time in Boston.

Thornton’s scrap with Scott was his third of the season. Thornton tangled with Krys Barch in the Bruins’ 4-3 shootout win over New Jersey on Tuesday. Thornton’s first fight was against the Rangers’ Mike Rupp in the season opener. Thornton fought 20 times last season.

In seven games, Thornton had one goal, zero assists, and 25 penalty minutes while averaging 4:52 of ice time.

Rookie Lane MacDermid will assume some of Thornton’s fighting responsibilities. MacDermid made his season debut on Thursday after being a healthy scratch for the first six games. MacDermid played only 4:12 while skating on the fourth line.

“It took a couple shifts to get back into the frame of mind of a game situation,” MacDermid said. “It was good to get my feet wet again.”

The 23-year-old MacDermid has six career NHL appearances. Last season, he fought Rupp in his NHL debut. During the lockout, MacDermid fought seven times in 32 games for Providence.

“I have a similar role as Shawn,” MacDermid said. “If situations arise out there where I need to step up, I’ll have to do that and fill in that role.”

MacDermid will have help. Milan Lucic and Adam McQuaid can throw down when necessary. Zdeno Chara might inquire with Scott on Feb. 10.

“We like to consider ourselves team tough,” Julien said. “We stick up for each other. You’ve seen [Andrew] Ference step in there at times. It’s not about one guy. It’s about our whole team. When I say team tough, it’s sticking up for each other. I think we’ve done that well. No doubt, Shawn’s going to be missed for all the right reasons, not the wrong ones.”

Paille stays home

The Bruins will also be without Daniel Paille for at least one game. Paille didn’t practice on Friday and didn’t travel with the team to Toronto.

Paille was high-sticked in the face by Tyler Myers in Thursday’s third period, and didn’t return. Julien classified Paille as having an upper-body injury.

“We’re going to deem it an upper-body injury, only for the reason that right now, we don’t have all the details,” Julien said.

Paille was playing on the third line with Chris Kelly and Rich Peverley for the first time this season. Paille assisted on Peverley’s second-period goal. Chris Bourque had been the No. 3 left wing for the first six games.

Tardif recalled

Jamie Tardif was recalled from Providence on an emergency basis. The 28-year-old will make his NHL debut against Toronto.

Tardif, who is from Toronto, is Providence’s leading scorer, with 21 goals and nine assists in 39 games. He will likely play on the fourth line on Saturday alongside MacDermid and Gregory Campbell.

“I’ve been waiting for a chance like this for a while,” Tardif said. “I’m going into my eighth year pro here. I’m just fortunate. At the same time excited going back to my hometown in Toronto. It’s definitely very exciting.”

The Bruins signed Tardif as a free agent on July 5, 2011. Last season, he had 15 goals and 15 assists in 57 games for Providence. This season, Tardif was one of six Providence players to participate in the Bruins’ shortened training camp.

“He’s got a really good shot,” Julien said. “Not only that, he’s a hard worker. He works hard both ways. He’s a good forechecker, a good backchecker, competes hard all the time. It’s nice to see those guys get rewarded for putting in all those years in the minors and finally getting a chance to play in the NHL. For him, there’s no doubt in my mind he’s earned it.”

Bourque back in

Bourque will return to the lineup against Toronto, likely playing on the third line. He was a healthy scratch on Thursday . . . Saturday’s game will mark the first time ex-Bruin Phil Kessel plays against both Tyler Seguin and Dougie Hamilton. Seguin, Hamilton, and Jared Knight are now Bruins because of the Kessel trade . . . David Krejci and Patrice Bergeron didn’t practice on Friday. They both will play on Saturday, Julien said . . . Upon reflection, Julien didn’t blame Lindy Ruff for calling his timeout after the Sabres made it a 7-4 game. Ruff switched out Thomas Vanek for Scott because MacDermid was on the ice. “Maybe the only thing I’m disappointed in is the fact that he thought I sent MacDermid out, if that’s his explanation,” Julien said. “Anybody who knows me knows better than that. I don’t do that in the last seconds. This isn’t my style. Nor is it wise to do those kinds of things. I just sent that line out to finish the game. But he wanted to be cautious. I’m not a coach who’ll send out a guy that can fight against the other team’s top player and beat him up with 20 seconds left.’’